• Advances in nano research
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• 제3권2호
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• pp.81-96
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• 2015

Octahedral shaped single crystalline undoped and Ga-doped indium oxide nano-and microcrystals were fabricated using vapor-solid growth process. Effects of Ga doping on the crystallinity, defect structure, and optical properties of the nano-/microstructures have been studied using scanning electron microscopy, microRaman spectroscopy, transmission electron microscopy and cathodoluminescence spectroscopy. It has been observed that incorporation of Ga does not affect the morphology of $In_2O_3$ structures due to its smaller ionic radius, and similar oxidation state as that of In. However, incorporation of Ga in high concentration (~3.31 atom %) causes lattice compression, reduces optical band gap and defect induced CL emissions of $In_2O_3$ nano-/microcrystals. The single crystalline Ga-doped, $In_2O_3$ nano-/microcrystals with low defect contents are promising for optoelectronic applications.

• 한국전기전자재료학회논문지
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• 제11권5호
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• pp.394-399
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• 1998

High power characteristics with vibration velocity were studied in $Pb(Y_{2/3}W_{1/3})O_3-Pb(Zr,Ti)O_3$(PYW-PZT) ceramics by using the constant current method. Young s modulus $Y_0^E$ and mechanical quality factor $Q_m$ are a function of the square of effective vibration velocity \upsilon_0$. The nonlinear proportional constants of the above functions indicate the degree of stability under the vibration level change. The stability of PYW-PZT ceramics estimated by these constants coincides with the results obtained through the heat generation. It was found that $Q_m$ was markedly decreased with increasing the vibration velocity, accompanying a lot of heat generation. The vibration hysteresis and dielectric loss according to the vibration velocity was reduced by doping $Fe_2O_3$to the ceramics. On the contrary, these losses was increased by doping $Nb_2O_5$.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.37-41
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• 2010

The authors investigated the photoluminescence (PL) and the electron paramagnetic resonance (EPR) from an magnesium (Mg)-doped GaN thin film with a delta-doped layer. The regularly doped sample shows a PL peak at 2.776 eV for the as-grown sample, and the peak shifts to 2.904 eV and increases in intensity for the annealed sample. The delta-doped sample also shows the same PL peak as does the regularly doped sample. However, only the annealed delta-doped layer shows a sharp EPR with a small isotropic Lande g-factor, $g_{II}$, of 2.029. This resonance is attributed to the delta-doped layer, which forms a hole-bound Mg-N atomic structure instead of the $Mg_{Ga}-V_N$ defect complex, indicating that the delta-doped sample was not optically activated to form PL centers but was instead electrically activated to form a hole-bound state.

• 전력전자학회논문지
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• 제24권6호
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• pp.411-418
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• 2019

Light-triggered thyristors (LTTs) are essential components in high-power applications, such as HVDC transmission and several pulsed-power applications. Generally, LTT fabrication includes a deep diffusion of aluminum as a p-type dopant to form a uniform p-base region, which needs careful concern for contamination and additional facilities in silicon semiconductor manufacturing factories. We fabricated 4-inch 5,000 V LTTs with boron implantation and diffusion process as a p-type dopant. The LTT contains a main cathode region, edge termination designed with a variation of lateral doping, breakover diode, integrated resistor, photosensitive area, and dV/dt protection region. The doping concentration of each region was adjusted with different doses of boron ion implantation. The fabricated LTTs showed good light triggering characteristics for a light pulse of 905 nm and a blocking voltage (V_DRM) of 6,500 V. They drove an average on-state current (I_TAVM) of 2,270 A, peak nonrepetitive surge current (I_TSM) of 61 kA, critical rate of rise of on-state current (di/dt) of 1,010 A/㎲, and limiting load integral (I²T) of 17 MA²s without damage to the device.

• 반도체디스플레이기술학회지
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• 제6권2호
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• pp.65-68
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• 한국전기전자재료학회논문지
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• 제29권12호
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• pp.759-763
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• 2016

We demonstrate the utilization of ion gel gate dielectrics for operating non-volatile transistor memory devices based on polymer semiconductor thin films. The gating process in typical electrolyte-gated polymer transistors occurs upon the penetration and escape of ionic components into the active channel layer, which dopes and dedopes the polymer film, respectively. Therefore, by controlling doping and dedoping processes, electrical current signals through the polymer film can be memorized and erased over a period of time, which constitutes the transistor-type memory devices. It was found that increasing the thickness of polymer films can enhance the memory performance of device including (i) the current signal ratio between its memorized state and erased state and (ii) the retention time of the signal.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.52-55
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• 2009

A red phosphor, $(Sr,Ca)_2P_2O_7:Eu^{2+},Mn^{2+}$, for UV-LED was synthesized under a reducing atmosphere, and its luminescent properties were investigated. The phosphor absorbs ultraviolet light at around 400 nm and efficiently emits red light at approximately 610 nm through an energy transfer from $Eu^{2+}$ to $Mn^{2+}$. Using the varied input current test for the phosphor-loaded LED lamps, it was found that the luminescent efficiency of the phosphor decreased with increasing light flux. This might be due to an increased probability of excited-state absorption and the consequent non-radiative relaxation in $Mn^{2+}$ ions in the condition of high photon influx.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.197-200
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• 1999

The polyacene materials prepared from phenol resine at relatively low temperature(550~75$0^{\circ}C$) show a highly Li-doped state up to $C_2$Li state without liberation of Li cluster. We prepared each polyacenic materials various temperature and investigated electrochemical property. We tried to change the mole ratio of [H]/[C] that was 0.24~0.4 range and finally found that the further discussion of improvements of battery materials. The X-ray structural analyses have shown that this material is essentiallly amorphous with loose structure in molecular size order. This structure ensures that the PAS battery has both reliability on repetitive doping-undoping processes and higher energy density than other batteries. The PAS electrode has been confirmed to show good stability and reversibility.

• Advances in Energy Research
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• 제2권2호
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• pp.97-104
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• 2014

A co-spray deposition technique has been developed to bypass a fundamental limitation in the conventional spray deposition technique, i.e., the deposition of metal oxides from incompatible precursors in the starting solution. With this technique, ZnO films codoped with F and Al have been successfully synthesized, in which F is incompatible with Al. Two starting solutions were prepared and co-sprayed through two separate spray heads. One solution contained only the F precursor, $NH_4F$. The second solution contained the Zn and Al precursors, $Zn(O_2CCH_3)_2$ and $AlCl_3$. The deposition was carried out at $500^{\circ}C$ on soda-lime glass in air. A minimum sheet resistance, $55.4{\Omega}/{\square}$, was obtained for Al and F codoped ZnO films after vacuum annealing at $400^{\circ}C$, which was lower than singly-doped ZnO with either Al or F. The transmittance for the codoped ZnO samples was above 90% in the visible range. This co-spray deposition technique provides a simple and cost-effective way to synthesize metal oxides from incompatible precursors with improved properties for photovoltaic applications.

• 한국광학회지
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• 제21권4호
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• pp.139-145
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• 2010

본 논문에서는 고농도로 도핑된 Bismuth 기반 어븀첨가 광섬유 증폭기의 이득 및 노이즈 특성을 정확히 예측하기 위하여 필요한 이론적 모델링 기법에 대한 연구를 수행 하였다. 고농도의 Erbium 이온이 첨가되었을 때 발생하는 Clustering 현상에 기인한 Inhomogeneous Broadening현상, Cooperative Upconversion 현상, Pump Excited State Absorption과 Signal Excited State Absorption 현상 등 모든 현상을 고려하여 6 레벨 증폭기 System Model을 제시하고 이를 전산모사하여 실험치와 비교함으로써 제시된 모델의 유효성을 검증하였다.